1. Technical Field
This application relates to electro-hydraulic forming processes and machines that are used to progressively form metal panels.
2. Background Art
Electro-hydraulic forming (EHF) is performed by providing a high voltage discharge in a liquid filled chamber that is directed toward a work piece such as a blank or a pre-formed panel. The work piece is formed into a one-sided die by the high voltage discharge.
One type of machine for EHF utilizes two electrodes that are connected to a bank of capacitors and assembled through the walls of a chamber that contains the liquid. This process may be referred to the gap discharge process. Some of the problems associated with a gap discharge process are that the electrodes erode, and the insulation may crack after several discharges. The electrodes require periodic maintenance and adjustment to compensate for electrode erosion and cracks in the insulation. As the quantity of energy discharged through the chamber increases, erosion of the electrodes and fracture of the insulation become more pronounced.
Another type of machine for EHF utilizes a thin wire that is placed in a liquid chamber and is connected between two electrodes. This process may be referred to as a wire discharge process. Some of the problems associated with the wire discharge process are that the wire must be replaced after each discharge, and the wire may weld to one of the electrodes or wire holders. The position of the wire is established relative to the initial position of the work piece.
The spacing between the electrodes and the work piece is either fixed or may increase if sequential discharges are used in a forming process. If sequential or multiple discharges are required to form a work piece, the distance between the wires and the work piece increases with each sequential discharge. As the distance increases, the power of the discharge decreases.
The volume of fluid in the chamber also increases due to the need to refill the chamber after each discharge. As the volume of fluid increases, the power of the discharge also decreases.
Applicant's disclosure addresses the above problems associated with electro-hydraulic forming as summarized below.